NCIt definition : The tissue of the pineal gland. The pineal gland is a small reddish-gray body, about
8 mm. in length which lies in the depression between the superior colliculi. It is
attached to the roof of the third ventricle near its junction with the mid-brain.
It develops as an outgrowth from the third ventricle of the brain. The pineal parenchyma
consists of follicles lined by epithelium and enveloped by connective tissues. It
produces and secretes melatonin.;